Field of the Invention
The invention relates to a method and a bus system for synchronizing a data exchange between one or more data sources and a control device.
When transferring data between clocked electrical assemblies, high-frequency transfer speeds and long bus lengths result in unavoidable time delays which can be outside one clock period. In this case, the data from a data source normally arrive at the data receiver later and later the further the distance between the data source and the receiver. The delay causes the synchronization of data signals and clock signals provided in the receiver to be lost.
A bus system normally has a control device for controlling the data transfer via the bus system. The bus systems are synchronized by providing data sources with delay elements which are used to delay the signals such that they can be synchronized to a clock signal, for example, when arriving at the control device.
The synchronization operation is performed with a control device by transmitting a synchronization signal, in response to which each of the data sources generates a response signal and returns it to the control device. The propagation time thus measured between transmission of the synchronization signal and reception of the response signal is approximately twice the signal propagation time via the bus system. The measured propagation time is converted into a delay-time used to delay outgoing signals in the respective data source in order to synchronize the latter to a reference clock. When the synchronization operation has ended, the latencies of all the data sources, i.e. the time after which data are available for further processing or forwarding in the control device, are not only known but also are identical for all the data sources connected in a bus system.